The highlighted photo was taken seconds after the fatal head-shot. It shows(top of frame) a hit team(spotter and shooter) in the Bryan Pergola. The fatal shot hit JFK, just as he was passing the Pergola. Coincidence? 25 yards from Pergola shooter to JFK, so a carbine(no scope) would have done the job nicely.
I've included the Nix film as well. Watch for the muzzle flash and smoke trail, from behind the pergola at the 13 second mark. One team in the pergola, one behind.